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  • richardmitnick 10:33 am on July 9, 2018 Permalink | Reply
    Tags: 'Breakthrough' algorithm exponentially faster than any previous one, John A Paulson School of Engineering and Applied Sciences   

    From John A Paulson School of Engineering and Applied Sciences: “‘Breakthrough’ algorithm exponentially faster than any previous one” 

    Harvard School of Engineering and Applied Sciences
    From John A Paulson School of Engineering and Applied Sciences

    7.9.18
    Leah Burrows

    Smarter, faster algorithm cuts number of steps to solve problems.

    1
    New algorithm uses adaptive sampling to exponentially speed up computation. No image credit.

    What if a large class of algorithms used today — from the algorithms that help us avoid traffic to the algorithms that identify new drug molecules — worked exponentially faster?

    Computer scientists at the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) have developed a completely new kind of algorithm, one that exponentially speeds up computation by dramatically reducing the number of parallel steps required to reach a solution.

    The theoretical research was presented at the ACM Symposium on Theory of Computing (STOC), June 25-29 and the experimental research will be presented at the International Conference on Machine Learning (ICML), July 10 -15.

    A lot of so-called optimization problems, problems that find the best solution from all possible solutions, such as mapping the fastest route from point A to point B, rely on sequential algorithms that haven’t changed since they were first described in the 1970s. These algorithms solve a problem by following a sequential step-by-step process. The number of steps is proportional to the size of the data. But this has led to a computational bottleneck, resulting in lines of questions and areas of research that are just too computationally expensive to explore.

    “These optimization problems have a diminishing returns property,” said Yaron Singer, Assistant Professor of Computer Science at SEAS and senior author of the research. “As an algorithm progresses, its relative gain from each step becomes smaller and smaller.”

    Singer and his colleague asked: what if, instead of taking hundreds or thousands of small steps to reach a solution, an algorithm could take just a few leaps?

    “This algorithm and general approach allows us to dramatically speed up computation for an enormously large class of problems across many different fields, including computer vision, information retrieval, network analysis, computational biology, auction design, and many others,” said Singer. “We can now perform computations in just a few seconds that would have previously taken weeks or months.”

    “This new algorithmic work, and the corresponding analysis, opens the doors to new large-scale parallelization strategies that have much larger speedups than what has ever been possible before,” said Jeff Bilmes, Professor in the Department of Electrical Engineering at the University of Washington, who was not involved in the research. “These abilities will, for example, enable real-world summarization processes to be developed at unprecedented scale.”

    Traditionally, algorithms for optimization problems narrow down the search space for the best solution one step at a time. In contrast, this new algorithm samples a variety of directions in parallel. Based on that sample, the algorithm discards low-value directions from its search space and chooses the most valuable directions to progress towards a solution.

    Take this toy example:

    You’re in the mood to watch a movie similar to The Avengers. A traditional recommendation algorithm would sequentially add a single movie in every step which has similar attributes to those of The Avengers. In contrast, the new algorithm samples a group of movies at random, discarding those that are too dissimilar to The Avengers. What’s left is a batch of movies that are diverse (after all, you don’t want ten Batman movies) but similar to The Avengers. The algorithm continues to add batches in every step until it has enough movies to recommend.

    This process of adaptive sampling is key to the algorithm’s ability to make the right decision at each step.

    “Traditional algorithms for this class of problem greedily add data to the solution while considering the entire dataset at every step,” said Eric Balkanski, a graduate student at SEAS and co-author of the research. “The strength of our algorithm is that in addition to adding data, it also selectively prunes data that will be ignored in future steps.”

    2
    The black line shows the number of steps a traditional algorithm takes to solve a problem while the red line demonstrates the number of steps the new algorithm needs. No image credit.

    In experiments, Singer and Balkanski demonstrated that their algorithm could sift through a data set which contained 1 million ratings from 6,000 users on 4,000 movies and recommend a personalized and diverse collection of movies for an individual user 20 times faster than the state-of-the-art.

    The researchers also tested the algorithm on a taxi dispatch problem, where there are a certain number of taxis and the goal is to pick the best locations to cover the maximum number of potential customers. Using a dataset of two million taxi trips from the New York City taxi and limousine commission, the adaptive-sampling algorithm found solutions 6 times faster.

    “This gap would increase even more significantly on larger scale applications, such as clustering biological data, sponsored search auctions, or social media analytics,” said Balkanski.

    Of course, the algorithm’s potential extends far beyond movie recommendations and taxi dispatch optimizations. It could be applied to:

    designing clinical trials for drugs to treat Alzheimer’s, multiple sclerosis, obesity, diabetes, hepatitis C, HIV and more
    evolutionary biology to find good representative subsets of different collections of genes from large datasets of genes from different species
    designing sensor arrays for medical imaging
    identifying drug-drug interaction detection from online health forums

    This process of active learning is key to the algorithm’s ability to make the right decision at each step and solves the problem of diminishing returns.

    “This research is a real breakthrough for large-scale discrete optimization,” said Andreas Krause, professor of Computer Science at ETH Zurich, who was not involved in the research. “One of the biggest challenges in machine learning is finding good, representative subsets of data from large collections of images or videos to train machine learning models. This research could identify those subsets quickly and have substantial practical impact on these large-scale data summarization problems.”

    Singer-Balkanski model and variants of the algorithm developed in the paper could also be used to more quickly assess the accuracy of a machine learning model, said Vahab Mirrokni, a principal scientist at Google Research, who was not involved in the research.

    “In some cases, we have a black-box access to the model accuracy function which is time-consuming to compute,” said Mirrokni. “At the same time, computing model accuracy for many feature settings can be done in parallel. This adaptive optimization framework is a great model for these important settings and the insights from the algorithmic techniques developed in this framework can have deep impact in this important area of machine learning research.”

    Singer and Balkanski are continuing to work with practitioners on implementing the algorithm.

    See the full article here .

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    Through research and scholarship, the Harvard School of Engineering and Applied Sciences (SEAS) will create collaborative bridges across Harvard and educate the next generation of global leaders. By harnessing the power of engineering and applied sciences we will address the greatest challenges facing our society.

    Specifically, that means that SEAS will provide to all Harvard College students an introduction to and familiarity with engineering and technology as this is essential knowledge in the 21st century.

    Moreover, our concentrators will be immersed in the liberal arts environment and be able to understand the societal context for their problem solving, capable of working seamlessly withothers, including those in the arts, the sciences, and the professional schools. They will focus on the fundamental engineering and applied science disciplines for the 21st century; as we will not teach legacy 20th century engineering disciplines.

    Instead, our curriculum will be rigorous but inviting to students, and be infused with active learning, interdisciplinary research, entrepreneurship and engineering design experiences. For our concentrators and graduate students, we will educate “T-shaped” individuals – with depth in one discipline but capable of working seamlessly with others, including arts, humanities, natural science and social science.

    To address current and future societal challenges, knowledge from fundamental science, art, and the humanities must all be linked through the application of engineering principles with the professions of law, medicine, public policy, design and business practice.

    In other words, solving important issues requires a multidisciplinary approach.

    With the combined strengths of SEAS, the Faculty of Arts and Sciences, and the professional schools, Harvard is ideally positioned to both broadly educate the next generation of leaders who understand the complexities of technology and society and to use its intellectual resources and innovative thinking to meet the challenges of the 21st century.

    Ultimately, we will provide to our graduates a rigorous quantitative liberal arts education that is an excellent launching point for any career and profession.

     
  • richardmitnick 12:37 pm on May 17, 2017 Permalink | Reply
    Tags: , Capasso Lab, Immersion microscopes, John A Paulson School of Engineering and Applied Sciences, Lithography, Metalenses, , , New lens   

    From Paulson: “Building a better microscope​” 

    Harvard School of Engineering and Applied Sciences
    Harvard John A. Paulson School of Engineering and Applied Sciences

    May 9, 2017
    Leah Burrows

    1
    Harvard researchers integrated an immersion meta-lens into a commercial scanning confocal microscope, achieving an imaging spatial resolution of approximately 200 nm. (Image courtesy of the Capasso Lab/Harvard SEAS)

    Metasurface could provide alternative to centuries-old technique.

    A team of researchers from the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) has developed the first flat lens for immersion microscopy. This lens, which can be designed for any liquid, may provide a cost-effective and easy-to-manufacture alternative to the expensive, centuries-old technique of hand polishing lenses for immersion objectives.

    The research is described in Nano Letters.

    “This new lens has the potential to overcome the drawbacks and challenges of lens-polishing techniques that have been used for centuries,” said Federico Capasso, the Robert L. Wallace Professor of Applied Physics and Vinton Hayes Senior Research Fellow in Electrical Engineering at SEAS, and senior author of the paper.

    When light hits an object, it scatters. Optical microscopes work by collecting that scattered light through a series of lenses and reconstructing it into an image. However, the fine detailed geometrical information of an object is carried by the portion of scattered light propagating with angles too large to be collected. Immersing the object in a liquid reduces the angles and allows for the capturing of light that was previously impossible, improving the resolving power of the microscope.

    Based on this principle, immersion microscopes use a layer of liquid — usually water or oil — between the specimen slide and the objective lens. These liquids have higher refractive indices compared to free space so the spatial resolution is increased by a factor equal to the refractive index of the liquid used.

    Immersion microscopes, like all microscopes, are comprised of a series of cascading lenses. The first, known as the front lens, is the smallest and most important component. Only a few millimeters in size, these semicircular lenses look like perfectly preserved rain drops.

    Because of their distinctive shape, most front lenses of high-end microscopes produced today are hand polished. This process, not surprisingly, is expensive and time-consuming and produces lenses that only work within a few specific refractive indices of immersion liquids. So, if one specimen is under blood and another underwater, you would need to hand-craft two different lenses.

    To simplify and speed-up this process, SEAS researchers used nanotechnology to design a front planar lens that can be easily tailored and manufactured for different liquids with different refractive indices. The lens is made up of an array of titanium dioxide nanofins and fabricated using a single-step lithographic process.

    2
    The array of titanium dioxide nanofins can be tailored for any immersion liquid (Image courtesy of Capasso Lab)

    “These lenses are made using a single layer of lithography, a technique widely used in industry,” said Wei Ting Chen, first author of the paper and postdoctoral fellow at SEAS. “They can be mass-produced with existing foundry technology or nanoimprinting for cost-effective high-end immersion optics.”

    Using this process, the team designed metalenses that can not only be tailored for any immersion liquid but also for multiple layers of different refractive indices. This is especially important for imaging biological material, such as skin.

    “Our immersion meta-lens can take into account the refractive indices of epidermis and dermis to focus light on the tissue under human skin without any additional design or fabrication complexity,” said Alexander Zhu, coauthor of the paper and graduate student at SEAS.

    “We foresee that immersion metalenses will find many uses not only in biological imaging but will enable entirely new applications and eventually outperform conventional lenses in existing markets,” said Capasso.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    Through research and scholarship, the Harvard School of Engineering and Applied Sciences (SEAS) will create collaborative bridges across Harvard and educate the next generation of global leaders. By harnessing the power of engineering and applied sciences we will address the greatest challenges facing our society.

    Specifically, that means that SEAS will provide to all Harvard College students an introduction to and familiarity with engineering and technology as this is essential knowledge in the 21st century.

    Moreover, our concentrators will be immersed in the liberal arts environment and be able to understand the societal context for their problem solving, capable of working seamlessly withothers, including those in the arts, the sciences, and the professional schools. They will focus on the fundamental engineering and applied science disciplines for the 21st century; as we will not teach legacy 20th century engineering disciplines.

    Instead, our curriculum will be rigorous but inviting to students, and be infused with active learning, interdisciplinary research, entrepreneurship and engineering design experiences. For our concentrators and graduate students, we will educate “T-shaped” individuals – with depth in one discipline but capable of working seamlessly with others, including arts, humanities, natural science and social science.

    To address current and future societal challenges, knowledge from fundamental science, art, and the humanities must all be linked through the application of engineering principles with the professions of law, medicine, public policy, design and business practice.

    In other words, solving important issues requires a multidisciplinary approach.

    With the combined strengths of SEAS, the Faculty of Arts and Sciences, and the professional schools, Harvard is ideally positioned to both broadly educate the next generation of leaders who understand the complexities of technology and society and to use its intellectual resources and innovative thinking to meet the challenges of the 21st century.

    Ultimately, we will provide to our graduates a rigorous quantitative liberal arts education that is an excellent launching point for any career and profession.

     
  • richardmitnick 9:23 am on March 8, 2017 Permalink | Reply
    Tags: , , , cure cancer, John A Paulson School of Engineering and Applied Sciences, , Push button,   

    From Paulson: Women in STEM – “Push button, cure cancer” Ph.D. candidates Nabiha Saklayen and Marinna Madrid 

    Harvard School of Engineering and Applied Sciences
    John A Paulson School of Engineering and Applied Sciences

    March 7, 2017
    Adam Zewe

    Two Harvard graduate students want to make curing blood cancer or HIV as easy as pressing a button.

    2
    Saklayen and Madrid are excited to move forward with their startup, Cellino. (Photo by Adam Zewe/SEAS Communications)

    1
    Cellino is a spinoff of the nanotechnology research being conducted in the Mazur lab. (Photo by Adam Zewe/SEAS Communications)

    Ph.D. candidates Nabiha Saklayen and Marinna Madrid have launched a startup to develop a simple, push-button device clinicians could use for gene therapy treatments. Their enterprise, Cellino, hopes to commercialize technology being developed in the lab of Eric Mazur, Balkanski Professor of Physics and Applied Physics at the John A. Paulson School of Engineering and Applied Sciences.

    The early-stage laboratory spinoff, which the pair launched in November, claimed first prize in the International Society for Optics and Photonics (SPIE) Startup Challenge, a pitch-off contest between more than 40 startups from around the world. In addition to winning $10,000 cash and $5,000 in optics products, Saklayen and Madrid were lauded for the impressive business potential of their startup.

    Their technique uses laser-activated nanostructures to deliver gene therapies directly into cells. When a laser is shined onto the nanostructures, the intense hot spots can open transient pores in nearby cells, Saklayen explained.

    “These pores are open long enough for any cargo that is around in the surrounding liquid to diffuse into the cell, and then the pores seal,” she said. “It is sort of like a magical opening where we can deliver molecules into the cell without damaging it, in a very targeted, quick way.”

    Developing effective intracellular delivery methods is a problem that has plagued biologists for decades, partly because the plasma membrane that surrounds a cell is selectively permeable and bars most molecules from entering.

    “Biologists have tried a number of different methods to do this, including viruses and chemical and physical processes, but none of them have been consistent enough and safe enough to be used reliably in treatments for blood disease,” said Madrid.

    The reliability of the nanostructure method developed at SEAS would give it a leg up over current practices. The biggest hurdle Madrid and Saklayen face now is translating the Mazur lab’s technology into a scalable, turnkey device.

    Their goal is to package the technology into a shoebox-sized device that contains everything a user needs—the laser, substrates, optical components, and computer interface. A user would put a patient’s cells and the nanofabricated chips into the device and use a touch screen to treat the cells, which could then be implanted into the patient.

    According to the Cellino team, those cells could be used to treat a number of different blood diseases, including HIV and blood cancers. By delivering gene-editing molecules into a patient’s hematopoietic stem cells, for instance, a clinician could repopulate a patient’s bone marrow with HIV-resistant cells. To treat cancers that affect the blood, the technology could be used to weaponize a patient’s T-cells, and then return them to the blood stream to attack the cancer.

    “What I find really exciting about this project is it is really pushing the barriers of what is the norm,” Saklayen said. “People talk about curing blood cancer all the time, but we have this unique opportunity to really enable that. That is the most inspiring part—we have an opportunity to make a difference in people’s lives. That is what drives me everyday to keep working hard.”

    As they move forward with Cellino, Saklayen and Madrid are working closely with Harvard’s Office of Technology Development (OTD), which has filed patent applications to secure the lab’s intellectual property and develop a viable commercialization strategy for the technology. Alan Gordon, a Director of Business Development in OTD, has been advising the team on how to develop a business plan and launch the company.

    After graduating from the Ph.D. program this spring, Saklayen will pursue Cellino full time. Madrid plans to graduate early so she can soon focus solely on the company, too. The co-founders have applied to a number of startup incubators and plan to enter additional pitch competitions to gain more validation for both their technology and their business plan.

    “There is definitely a production challenge when you talk about making things at a larger scale, but we are making good progress,” Madrid said. “The technology is very powerful because it is so streamlined. Now it is all about packaging.”

    Mazur is proud of his students’ accomplishments and excited for the potential of their startup. “This work is really transformative and opens the door to new therapies for currently incurable diseases,” he said.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    Through research and scholarship, the Harvard School of Engineering and Applied Sciences (SEAS) will create collaborative bridges across Harvard and educate the next generation of global leaders. By harnessing the power of engineering and applied sciences we will address the greatest challenges facing our society.

    Specifically, that means that SEAS will provide to all Harvard College students an introduction to and familiarity with engineering and technology as this is essential knowledge in the 21st century.

    Moreover, our concentrators will be immersed in the liberal arts environment and be able to understand the societal context for their problem solving, capable of working seamlessly withothers, including those in the arts, the sciences, and the professional schools. They will focus on the fundamental engineering and applied science disciplines for the 21st century; as we will not teach legacy 20th century engineering disciplines.

    Instead, our curriculum will be rigorous but inviting to students, and be infused with active learning, interdisciplinary research, entrepreneurship and engineering design experiences. For our concentrators and graduate students, we will educate “T-shaped” individuals – with depth in one discipline but capable of working seamlessly with others, including arts, humanities, natural science and social science.

    To address current and future societal challenges, knowledge from fundamental science, art, and the humanities must all be linked through the application of engineering principles with the professions of law, medicine, public policy, design and business practice.

    In other words, solving important issues requires a multidisciplinary approach.

    With the combined strengths of SEAS, the Faculty of Arts and Sciences, and the professional schools, Harvard is ideally positioned to both broadly educate the next generation of leaders who understand the complexities of technology and society and to use its intellectual resources and innovative thinking to meet the challenges of the 21st century.

    Ultimately, we will provide to our graduates a rigorous quantitative liberal arts education that is an excellent launching point for any career and profession.

     
  • richardmitnick 9:32 am on October 26, 2016 Permalink | Reply
    Tags: John A Paulson School of Engineering and Applied Sciences, , Scheduling algorithm for LSST   

    From Harvard John A Paulson School of Engineering and Applied Sciences: “Eye on the sky” 

    Harvard School of Engineering and Applied Sciences
    harvard John A Paulson School of Engineering and Applied Sciences

    October 26, 2016
    Adam Zewe

    Student uses computer science to chart a course for massive telescope

    When it begins operating in 2022, the $500 million Large Synoptic Survey Telescope (LSST) will capture some of the sharpest night sky images ever produced, giving scientists an unprecedented view of near-Earth asteroids, supernovae, and the Milky Way galaxy.

    But the telescope, under construction atop a peak is Chile’s northern Andes, also presents an unprecedented challenge for astrophysicists—it will require a complicated scheduling algorithm to determine where to point the telescope as it traces the sky. To Harvard student Daniel Rothchild, that sounded like a puzzle he could solve.

    “This is not a well-studied problem in astrophysics because there has never been a telescope that behaved like this,” said Rothchild, A.B. ’17, a physics concentrator who is pursing a secondary in computer science at the John A. Paulson School of Engineering and Applied Sciences. “But scheduling is a well-studied problem in computer science. It is very important that the scheduler be effective, or the telescope is not going to be looking at the places that will yield the best data.”

    Working with Christopher Stubbs, Samuel C. Moncher Professor of Physics and Astronomy, who is a contributor to the LSST project, Rothchild launched an independent research project to develop a scheduling algorithm that would be effective in this unique situation.

    LSST/Camera, built at SLAC
    LSST/Camera, built at SLAC
    LSST Interior
    LSST telescope, currently under construction at Cerro Pachón Chile
    LSST telescope, currently under construction at Cerro Pachón Chile

    The LSST, which will image the entire night sky every three days, will stop at each point for 30 seconds before moving onto a new field. Longer calculation time leads to a much more complicated algorithm and that could easily bog down the telescope’s progress. The algorithm must also overcome the challenge of determining the “best” place for the telescope to look, when there are literally 10 billion possibilities.

    “How do you decide if Milky Way astronomy is more important than asteroid science on this particular 30-second exposure?” Rothchild asked. “It’s very difficult for scientists to say, here’s an exact quantification of how important these different areas are.”

    Rather than using machine-learning or mathematical merit functions to determine the ideal next field, Rothchild is writing code that will give the telescope a baseline optimal path to follow, along with instructions for how to respond when faced with adverse weather and unexpected downtime.

    Programming a set path for the entire 10-year span of the project allows scientists to explicitly optimize global properties of the telescope’s data, instead of hoping the merit functions or machine-learning algorithms will perform those optimizations themselves, he said. It also eliminates the headaches of trying to determine why the computer pointed the telescope at a certain location, or troubleshooting a machine-learning algorithm that seems to be aiming the telescope far off the best course.

    “There are certain astronomical elements that are fixed, even 10 years out. We know the moon will be moving a certain way and the stars will appear in specific patterns and locations, and we also know the meridian is generally the best place to point the telescope because there is the least amount of air overhead,” he said. “By programming these considerations into the scheduler explicitly, I hope to create an algorithm that will produce better schedules than those produced with existing methods.”

    His code lays out a path for the telescope to follow using a combination of astronomical data and meteorological predictions. Rothchild’s method involves much faster calculations than other scheduler algorithms because there are no machine-learning elements.

    Several other researchers are working on schedulers, and all have taken a slightly different approach. Once the telescope hardware is complete, the LSST leadership team will test each scheduler and select the one to use.

    Though he still has six years to wait before the LSST has its eye on the sky, Rothchild is excited for the opportunity to contribute to such a significant astrophysics project.

    “The LSST will produce about 15 terabytes of data each night for 10 years. By comparison, the Hubble telescope produces 10 terabytes of data in one year,” he said. “This project is going to enable scientists to take precision measurements of the universe in an unprecedented way. It is very cool to be a part of that.”

    1
    Currently under construction in Chile, the LSST will incorporate the world’s largest digital camera. (Photo credit: LSST.)

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    Through research and scholarship, the Harvard School of Engineering and Applied Sciences (SEAS) will create collaborative bridges across Harvard and educate the next generation of global leaders. By harnessing the power of engineering and applied sciences we will address the greatest challenges facing our society.

    Specifically, that means that SEAS will provide to all Harvard College students an introduction to and familiarity with engineering and technology as this is essential knowledge in the 21st century.

    Moreover, our concentrators will be immersed in the liberal arts environment and be able to understand the societal context for their problem solving, capable of working seamlessly withothers, including those in the arts, the sciences, and the professional schools. They will focus on the fundamental engineering and applied science disciplines for the 21st century; as we will not teach legacy 20th century engineering disciplines.

    Instead, our curriculum will be rigorous but inviting to students, and be infused with active learning, interdisciplinary research, entrepreneurship and engineering design experiences. For our concentrators and graduate students, we will educate “T-shaped” individuals – with depth in one discipline but capable of working seamlessly with others, including arts, humanities, natural science and social science.

    To address current and future societal challenges, knowledge from fundamental science, art, and the humanities must all be linked through the application of engineering principles with the professions of law, medicine, public policy, design and business practice.

    In other words, solving important issues requires a multidisciplinary approach.

    With the combined strengths of SEAS, the Faculty of Arts and Sciences, and the professional schools, Harvard is ideally positioned to both broadly educate the next generation of leaders who understand the complexities of technology and society and to use its intellectual resources and innovative thinking to meet the challenges of the 21st century.

    Ultimately, we will provide to our graduates a rigorous quantitative liberal arts education that is an excellent launching point for any career and profession.

     
  • richardmitnick 10:19 am on October 17, 2016 Permalink | Reply
    Tags: , , John A Paulson School of Engineering and Applied Sciences, , ,   

    From John A Paulson School of Engineering and Applied Sciences: “A new spin on superconductivity” 

    Harvard School of Engineering and Applied Sciences
    John A Paulson School of Engineering and Applied Sciences

    October 14, 2016
    Leah Burrows

    1

    Researchers from the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) have made a discovery that could lay the foundation for quantum superconducting devices. Their breakthrough solves one the main challenges to quantum computing: how to transmit spin information through superconducting materials.

    Every electronic device — from a supercomputer to a dishwasher — works by controlling the flow of charged electrons. But electrons can carry so much more information than just charge; electrons also spin, like a gyroscope on axis.

    Harnessing electron spin is really exciting for quantum information processing because not only can an electron spin up or down — one or zero — but it can also spin any direction between the two poles. Because it follows the rules of quantum mechanics, an electron can occupy all of those positions at once. Imagine the power of a computer that could calculate all of those positions simultaneously.

    A whole field of applied physics, called spintronics, focuses on how to harness and measure electron spin and build spin equivalents of electronic gates and circuits.

    By using superconducting materials through which electrons can move without any loss of energy, physicists hope to build quantum devices that would require significantly less power.

    But there’s a problem.

    According to a fundamental property of superconductivity, superconductors can’t transmit spin. Any electron pairs that pass through a superconductor will have the combined spin of zero.

    In work published recently in Nature Physics, the Harvard researchers found a way to transmit spin information through superconducting materials.

    “We now have a way to control the spin of the transmitted electrons in simple superconducting devices,” said Amir Yacoby, Professor of Physics and of Applied Physics at SEAS and senior author of the paper.

    It’s easy to think of superconductors as particle super highways but a better analogy would be a super carpool lane as only paired electrons can move through a superconductor without resistance.

    These pairs are called Cooper Pairs and they interact in a very particular way. If the way they move in relation to each other (physicists call this momentum) is symmetric, then the pair’s spin has to be asymmetric — for example, one negative and one positive for a combined spin of zero. When they travel through a conventional superconductor, Cooper Pairs’ momentum has to be zero and their orbit perfectly symmetrical.

    But if you can change the momentum to asymmetric — leaning toward one direction — then the spin can be symmetric. To do that, you need the help of some exotic (aka weird) physics.

    Superconducting materials can imbue non-superconducting materials with their conductive powers simply by being in close proximity. Using this principle, the researchers built a superconducting sandwich, with superconductors on the outside and mercury telluride in the middle. The atoms in mercury telluride are so heavy and the electrons move so quickly, that the rules of relativity start to apply.

    “Because the atoms are so heavy, you have electrons that occupy high-speed orbits,” said Hechen Ren, coauthor of the study and graduate student at SEAS. “When an electron is moving this fast, its electric field turns into a magnetic field which then couples with the spin of the electron. This magnetic field acts on the spin and gives one spin a higher energy than another.”

    So, when the Cooper Pairs hit this material, their spin begins to rotate.

    “The Cooper Pairs jump into the mercury telluride and they see this strong spin orbit effect and start to couple differently,” said Ren. “The homogenous breed of zero momentum and zero combined spin is still there but now there is also a breed of pairs that gains momentum, breaking the symmetry of the orbit. The most important part of that is that the spin is now free to be something other than zero.”

    The team could measure the spin at various points as the electron waves moved through the material. By using an external magnet, the researchers could tune the total spin of the pairs.

    “This discovery opens up new possibilities for storing quantum information. Using the underlying physics behind this discovery provides also new possibilities for exploring the underlying nature of superconductivity in novel quantum materials,” said Yacoby.

    This research was coauthored by Sean Hart, Michael Kosowsky, Gilad Ben-Shach, Philipp Leubner, Christoph Brüne, Hartmut Buhmann, Laurens W. Molenkamp and Bertrand I. Halperin.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    Through research and scholarship, the Harvard School of Engineering and Applied Sciences (SEAS) will create collaborative bridges across Harvard and educate the next generation of global leaders. By harnessing the power of engineering and applied sciences we will address the greatest challenges facing our society.

    Specifically, that means that SEAS will provide to all Harvard College students an introduction to and familiarity with engineering and technology as this is essential knowledge in the 21st century.

    Moreover, our concentrators will be immersed in the liberal arts environment and be able to understand the societal context for their problem solving, capable of working seamlessly withothers, including those in the arts, the sciences, and the professional schools. They will focus on the fundamental engineering and applied science disciplines for the 21st century; as we will not teach legacy 20th century engineering disciplines.

    Instead, our curriculum will be rigorous but inviting to students, and be infused with active learning, interdisciplinary research, entrepreneurship and engineering design experiences. For our concentrators and graduate students, we will educate “T-shaped” individuals – with depth in one discipline but capable of working seamlessly with others, including arts, humanities, natural science and social science.

    To address current and future societal challenges, knowledge from fundamental science, art, and the humanities must all be linked through the application of engineering principles with the professions of law, medicine, public policy, design and business practice.

    In other words, solving important issues requires a multidisciplinary approach.

    With the combined strengths of SEAS, the Faculty of Arts and Sciences, and the professional schools, Harvard is ideally positioned to both broadly educate the next generation of leaders who understand the complexities of technology and society and to use its intellectual resources and innovative thinking to meet the challenges of the 21st century.

    Ultimately, we will provide to our graduates a rigorous quantitative liberal arts education that is an excellent launching point for any career and profession.

     
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